Mental health clinicians working in emergency crisis assessment teams or mental health triage roles are required to make rapid and accurate risk assessments. The assessment of violence risk at triage is particularly pertinent to the early identification and prevention of patient violence, and to enhancing the safety of clinical staff and the general public. To date, the evidence base for mental health triage violence risk assessment has been minimal. This study aimed to address this evidence gap by identifying best available evidence for mental health-related risk factors for patient-initiated violence. We conducted a systematic review based on the National Health and Medical Research Council of Australia's methodology for systematic reviews. A total of 6847 studies were retrieved, of which 326 studies met the study inclusion criteria. Of these studies, 277 met inclusion criteria but failed the quality appraisal process, thus a total of 49 studies were included in the final review. The risk factors that achieved the highest evidence grading were predominantly related to dynamic clinical factors immediately observable in the patient's general appearance, behaviour and speech. These factors included hostility/anger, agitation, thought disturbance, positive symptoms of schizophrenia, suspiciousness and irritability.